From 62207228f717d0eb29aca5d1fbc155f151d6814e Mon Sep 17 00:00:00 2001 From: Teruaki Kawashima Date: Sun, 16 Jan 2011 12:45:11 +0000 Subject: image viewer: add quick guide describing how to add image decoder. also improve comments. git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29066 a1c6a512-1295-4272-9138-f99709370657 --- apps/plugins/imageviewer/imageviewer.h | 21 +++++++++++-------- apps/plugins/imageviewer/readme.txt | 37 ++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 8 deletions(-) create mode 100644 apps/plugins/imageviewer/readme.txt (limited to 'apps') diff --git a/apps/plugins/imageviewer/imageviewer.h b/apps/plugins/imageviewer/imageviewer.h index 504ef2bb3a..f35c1c7e6d 100644 --- a/apps/plugins/imageviewer/imageviewer.h +++ b/apps/plugins/imageviewer/imageviewer.h @@ -469,19 +469,24 @@ struct imgdec_api { /* functions need to be implemented in each image decoders. */ struct image_decoder { - /* if unscaled image can be always displayed when there isn't enough memory - * for resized image. e.g. when using native format to store image. */ + /* set true if unscaled image can be always displayed even when there isn't + * enough memory for resized image. e.g. when using native format to store + * image. */ const bool unscaled_avail; - /* return needed size of buffer to store downscaled image by ds */ + /* return needed size of buffer to store downscaled image by ds. + * this is used to calculate min downscale. */ int (*img_mem)(int ds); - /* load image from filename. set width and height of info properly. also, set - * buf_size to remaining size of buf after load image. it is used to caluclate - * min downscale. */ + /* load image from filename. use the passed buffer to store loaded, decoded + * or resized image later, so save it to local variables if needed. + * set width and height of info properly. also, set buf_size to remaining + * size of buf after load image. it is used to calculate min downscale. + * return PLUGIN_ERROR for error. ui will skip to next image. */ int (*load_image)(char *filename, struct image_info *info, unsigned char *buf, ssize_t *buf_size); - /* downscale loaded image by ds. note that buf to store reszied image is not - * provided. return PLUGIN_ERROR for error. ui will skip to next image. */ + /* downscale loaded image by ds. use the buffer passed to load_image to + * reszie image and/or store resized image. + * return PLUGIN_ERROR for error. ui will skip to next image. */ int (*get_image)(struct image_info *info, int ds); /* draw part of image */ void (*draw_image_rect)(struct image_info *info, diff --git a/apps/plugins/imageviewer/readme.txt b/apps/plugins/imageviewer/readme.txt new file mode 100644 index 0000000000..b7ec71e7be --- /dev/null +++ b/apps/plugins/imageviewer/readme.txt @@ -0,0 +1,37 @@ +this document describes how to add new image decoder. + +1. create a directory which name is your image decoder's name and put source files + under the directory. +'const struct image_decoder image_decoder' and 'IMGDEC_HEADER' must be declared in + one of your source files. +see imageviewer.h for the detail of struct image_decoder. + +2. add the directory name to apps/plugins/imageviewer/SUBDIR so that the decoder + is built. +if the decoder is supported by particular targets, surround it with #if directive. +e.g. if the decoder supports color LCD targets only, +#ifdef HAVE_LCD_COLOR +bmp +#endif + +3. append appropriate entry to enum image_type in image_decoder.h, decoder_names + and ext_list in image_decoder.c so that the imageviewer plugin can recognize + the decoder. +if the decoder is supported by particular targets, surround them with same #if + directive in SUBDIR. + +4. add entry to apps/plugins/viewers.config + (in format: file_extension,viewer/imageviewer) so that the file with specified + file extension will be opened by image viewer plugin. +if the decoder is supported by particular targets, surround it with same #if + directive in SUBDIR. + +5. add entry to apps/plugins/CATEGORIES (in format: decoder_name,viewer) so + that the build file is copied to viewers directory. +DON'T surround this with #if directive. + + +notes: +if you need to use greylib functions to draw image, add the functions to + struct imgdec_api just like gray_bitmap_part because GREY_INFO_STRUCT is + declared in imageviewer and is not available from the decoder. -- cgit v1.2.3